1. Field of the Invention
The present invention relates to a broadcast communication system in which one or Radio Frequencies (RFs) are used to carry multiple services, and more particularly to a method and apparatus for transmitting/receiving control information for a frame including multiple services.
2. Description of the Related Art
In the information society of the 21st century, the age of digital, multi-channel, broadband, and high-quality broadcast communication services has begun in earnest. In particular, with the recent popularization of High Definition digital TeleVisions (HD digital TVs) and Portable Multimedia Players (PMPs), there is an increasing demand for digital broadcast services supporting various reception schemes.
In compliance with such a demand, the 2nd Generation European terrestrial digital broadcast standard, the DVB-T2 (Digital Video Broadcasting-Terrestrial), is currently under standardization for three reception schemes, that is, a reception scheme reutilizing the conventional digital receive antenna for home use (fixed-type), a reception scheme using a multi-antenna for capacity enhancement, and a reception scheme for a mobile terminal (mobile-type). In contrast with the 1st Generation European terrestrial digital broadcast standard, the DVB-T/H, which considers only two reception schemes, that is, the fixed-type and mobile-type reception schemes, the DVB-T2 adds the reception scheme using a multi-antenna to the two reception schemes, and is considering changes in a physical layer structure and control information according thereto.
In such a physical layer structure, a control message regarding a transmission scheme in each physical layer is transmitted over a control channel. For example, suppose that a signal is transmitted in units of frames, multiple services may constitute one frame, and the frame includes a service index, location information, a modulation scheme/code rate, a cell D for each service. Also, since service configuration information and its related information may vary from frame to frame, the control channel is transmitted separately from a data channel in each frame.
FIG. 1 illustrates a scheme of transmitting/receiving broadcast services in a Fixed Frequency (FF) mode, which represents the conventional 1st generation broadcast communication system.
Referring to FIG. 1, a transmitter transmits broadcast services through multiple RFs (RF 1 to RF 4) carrying different services (service 1 to service 10). A receiver receives a desired service by tuning to an RF carrying the desired service. For example, when the receiver is to receive service 1, the receiver acquires location information and a modulation/coding scheme for service 1 by tuning to RF 1, and then demodulates service 1.
FIG. 2A illustrates a scheme of transmitting/receiving broadcast services in the conventional 2nd generation broadcast communication system.
Referring to FIG. 2, a transmitter divides a service (each service in FIG. 1), which is in the form of a long packet, into a plurality of short sub-slots, and transmits the service in the form of the divided sub-slots through multiple RFs (RF 1 to RF 4) used to carry the service. A receiver tracks the location of the desired service in each RF containing the desired service through control information, and receives the corresponding service. As illustrated in FIG. 2A, when the receiver receives service 1, the receiver demodulates the corresponding service in the order of RF 1, RF 4. RF 3, and RF 2 according to the sequence in which sub-slots of the corresponding service can be received in the time domain. Thus, in the scheme of transmitting/receiving broadcast services in the conventional 2nd Generation broadcast communication system, even when the same amount of services are transmitted, a small amount of data is transmitted through multiple RFs, as compared to when a large amount of data is transmitted at a time using a fixed RF for each service, so that time and frequency diversity gains can be expected. Such a frame configuration scheme is called Time-Frequency Slicing (TFS).
FIG. 2B illustrates a transfer frame format of convention TFS.
In the transfer frame format illustrated in FIG. 2B, ten service packets are transmitted through multiple RFs (RF 1 to RF 4). This TFS frame may be configured by allocating all service packets to one RF and arranging all of the service packets in an adjacent RF in such a manner as to be cyclically shifted. When four RFs are used as illustrated in FIG. 2B, each service basically uses four sub-slots because one service is transmitted through the four RFs, but may use five sub-slots due to cyclic shifting, as in the case of service 3.
Also, in FIG. 2B, signal P1 may be used as a preamble for time synchronization, and signal P2 carries control information for each service in the current or next frame. The control information includes location information regarding points of time at which each service begins and ends within a frame, and others. In particular, the location information for each service may be transmitted while being included not in signal P2 but in each service traffic. In such a case, it does not matter if signal P2 is not read during continuous reception of the same service.
However, when a receiver continues to receive a service, and then changes the current service channel to a different service channel, the receiver must acquire control information for a service corresponding to the different service channel in order to receive the service of the different service channel.
Therefore, there is a need for a method to efficiently transmit/receive control information for a target service of a service change so that the target service can be received when the service change occurs in a receiver.